All authors read and approved the final manuscript.”“Background Tuberculosis (TB) remains a major cause of morbidity and mortality, particularly in developing countries, and is considered a serious public health problem worldwide, killing almost 2 million

people every year [1]. According to the WHO, one-third of the world’s population is infected with Mycobacterium tuberculosis (Mtb). The incidence of new cases of TB has increased mainly due to the impact of the HIV epidemic [2] and the emergence of resistance to anti-TB drugs [3]. The currently available vaccine, Mycobacterium bovis bacillus Calmette-Guérin (BCG), is one of the oldest and most commonly administered vaccines worldwide [4]. It was obtained in the early 1920′s by Albert Calmette and Camille Guérin at the Pasteur Institute, Lille, France, after 231 serial passages of a clinical Napabucasin isolate of M. bovis in glycerinated medium containing ox bile [5]. Attenuation

during in vitro Suplatast tosilate passages is believed to have resulted from the loss and/or reorganization of genomic regions, some of which have been recently identified [6–9]. M. bovis BCG Moreau is the strain used in Brazil for CFTRinh-172 mw vaccine production since the 1930′s [10]. According to recent molecular studies [11], it is considered an “”old”" strain, more similar to the original BCG derived by Calmette and Guérin. Vaccination with BCG has many advantages, yielding efficient protection against severe childhood forms of TB, and also against leprosy [12]. In addition, it is recognized as a safe and inexpensive vaccine that can be administered shortly after birth [13, 14]. On the other hand, it shows variable protection against the most common form of the disease, pulmonary tuberculosis in adults, and it does not prevent the establishment of latent TB. It has been reported that different M. bovis BCG strains, including BCG Moreau, induce varying levels of protection against M. tuberculosis infection in animal models [15]. Comparative genetic analysis of BCG strains has revealed that each vaccine currently in use is unique [11], and providing several clues for the failure of BCG as an effective vaccine.